The present invention relates to a process for the manufacture of sandwich laminates by applying a wet laminate of an uncured resin-impregnated glass mat to the wall of a mold cavity and introducing into the closed mold cavity a free-flowing reaction mixture forming a rigid foamed plastic. The invention is also directed to the sandwich laminates so-produced. The laminates of the present invention are particularly useful as skis.
It is known to manufacture sandwich laminates, and especially skis, by introducing a dry laminate and other inserted parts into a mold cavity. After the mold is closed, a reaction mixture which forms a rigid foamed plastic, especially polyurethane-based, or a polystyrene granular material is introduced into the mold and allowed to expand to a rigid foamed plastic core. The adhesion between laminate and rigid foamed plastic core is not particularly good, so that this process cannot be used for manufacturing highly stressed sandwich laminates.
According to another known process a wet laminate is built up around a prefabricated rigid foam plastic core to form a composite which is then molded. This procedure, which is associated with much manual work, is very expensive. The adhesion of the laminate to the foamed plastic core depends on manual skills.
If a wet laminate were used with a foamable reaction mixture, there is also a risk that the reaction mixture would mix with the wet laminate, i.e., the wet laminate would become permeated. As a result, the desired laminate layer would become weakened, even though there would presumably be a very good adhesion between the foamed plastic core and the laminate.
The problem exists of discovering a process wherein the laminate survives as a separate layer and flows well round inserts which may be present during the molding. In addition, a good adhesion must develop in the finished part between foamed plastic core and laminate, and the finished part must be able to withstand quite high stress.